Combining hydrothermal-alkaline/oxygen pretreatment of reed with PEG 6,000-assisted enzyme hydrolysis promote bioethanol fermentation and reduce enzyme loading

Abstract

This study aimed to gain high bioethanol yield and concentration using reed as a raw material at a low enzyme loading to reduce its production cost. Reed was pretreated with liquid hot water–alkaline/oxygen (LHW–NaOH/O2), and then hydrolyzed at a cellulase loading of 3 fiter paper units/g–substrate with polyethylene glycol (PEG) 6000 to promote fermentation. Approximately 40.2 g/L of bioethanol concentration and 83.7 % (w/w) yield were achieved via separate hydrolysis and fermentation under optimal conditions. PEG 6000 was effective for promoting a high reed-to-bioethanol conversion at a low enzyme loading in the presence of a LHW–NaOH/O2 pretreated substrate. Enzyme dosage in the treatment with PEG 6000 decreased by 88 % compared with that in the treatment without PEG 6,000. The total cost decreased by 72.8 % compared with fed-batch semi-simultaneous saccharification and fermentation. Hence, separate hydrolysis and fermentation with PEG 6000 added method was recommended for LHW–NaOH/O2 pretreatment. This study provided an optimal reed-to-bioethanol conversion with a reduced production cost.